No disrespect Paul, but why not use blender...
Just look at the features:
http://www.quadsoftware.com/index.php?m=.../features_videoI doubt that Blender calculates terrain with fractal algorithms or applies natural erosion for you. And then there is procudural mapping and texturing, depending on parameters like altitude, slope and more. There is a terrain LOD edit mode, you can paint layers like vegetation or water.
And you do all this in real-time.
By the way: I did not find any comment towards Gamestudio except a remark that they want to support Ogre and 3D Game Engine soon. Maybe it is a typo though.
